Spring Yarg Integration

I just announced the new Spring 5 modules in REST With Spring:

1. Overview

Yet Another Report Generator (YARG) is an open source reporting library for Java, developed by Haulmont. It allows creating templates in most common formats (.doc, .docs, .xls, .xlsx, .html, .ftl, .csv) or custom text formats and filling it with data loaded by SQL, Groovy, or JSON.

In this article, we’re going to demonstrate how to use a Spring @RestController that outputs a .docx document with JSON-loaded data.

2. Setting up the Example

In order to start using YARG, we need to add the following dependencies to our pom:

The ReportBuilder class is going to be responsible for the creation of the report, grouping up the template and the data. ReportTemplateBuilder loads our previously defined Letter.docxtemplate by specifying the path, name, and output-type of the document.

Then we’ll add the loaded template to the report builder.

Now we need to define the data that is going to be inserted in the document, this will be a Data.json file with the following:

Here we define a BandBuilder in order to create a ReportBand, which is the abstraction that YARG uses for the groups of data that we defined earlier in the template document.

We can see that we define the name with the exact same section “Main”, then we use a query method to find the “Main” section and declare a parameter that will be used to find the data needed to fill the template.

It’s important to note that YARG uses JsonPath to traverse the JSON, which is why we see this “$.main” syntax.

Next, let’s specify in the query that the format of the data is “json”, then add the band to the report and finally, build it.

The last step is to define the Reporting object, which is responsible for inserting the data into the template and generate the final document:

We use a DefaultFormatterFactory that supports the common formats listed at the beginning of the article. After that, we set the JsonDataLoader that is going to be responsible for parsing the JSON.

In the final step, we set the appropriate content type for the .docx format and run the report. This will wire up the JSON data and insert it into the template outputting the result into the response output stream.

Now we can access the /generate/doc URL to download the document and we shall see the following result in our generated .docx:

4. Conclusion

In this article, we showed how we can easily integrate YARG with Spring and use its powerful API to create documents in a simple way.

We used JSON as the data input, but Groovy and SQL are also supported.

If you want to learn more about it you can find the documentation here.